Control systems of various types have been used for many years to effect gear changes in motor transmissions by imposing both pushing and pulling forces upon the transmission gear change mechanism. Such systems are disclosed for example in U.S. Pat. No. 1,490,206 where shift bars are pushed and pulled by a pivotally mounted lever arm to effect a change in gears of a motor vehicle transmission. U.S. Pat. No. 2,847,871 discloses a shifting mechanism similar to that disclosed in U.S. Pat. No. 1,490,206 with the addition of a positive lock and detent mechanism for the shift rods that holds the balance of the shift rods in a fixed position when one of the rods is being pushed or pulled.
Examples of transmission control mechanisms utilizing a single control cable that is pushed and pulled to effect a transmission gear change are disclosed respectively in U.S. Pat. Nos. 2,847,874 and 3,520,208. Examples of transmission control systems that feature two push rods and two control cables that are both pushed and pulled to effect a transmission gear change are disclosed respectively in U.S. Pat. Nos. 2,961,890 and 2,917,941.
The above described transmission control mechanisms are typical of the art up to the time of the present invention in that all require that both pushing and pulling forces of some type be transmitted through the connecting members to the transmission gear change mechanism to effect a change in the transmission gears and are unable to effect a change to all of the other gear positions by applying only tensional pulling forces alone to the transmission gear change mechanism. The transmission control system of the present invention eliminates the need to apply pushing forces to the transmission gear change mechanism and applys only tensional pulling forces to effect a change of gears in a motor transmission to any one of a plurality of gear positions. The elimination of the requirement of having to impose pushing forces upon the force transmitting connecting members is particularly advantageous where flexible cables are used as the connecting members since flexible cables are subject to backlash when the force applied to the cables is reversed from a pushing force to a tensional pulling force.